Take small fresh-gathered button mushrooms, peel them carefully with a penknife, and cut off the stems; throwing the mushrooms into salt and water as you do them. Then put them into a porcelain skillet of fresh water, cover it closely, and set it over a quick fire. Boil it as fast as possible for seven or eight minutes, not more. Take out the mushrooms, drain them, and spread them on a clean board, with the bottom or hollow side of each mushroom turned downwards. Do this as quickly as possible, and immediately, while they are hot, sprinkle them over with salt. When they are cold, put them into a glass jar with slight layers of mace and sliced ginger. Fill up the jar with cold cider vinegar. Put a spoonful of sweet oil on the top of each jar, and cork it closely.